Overcurrent or excess current is a situation where a larger than intended electrical current flows through a conductor, leading to excessive generation of heat and the risk of damaging infrastructure, equipment and causing fires. Possible causes for overcurrent include short circuits, excessive load, and incorrect design. To protect against these hazards, devices such as circuit breakers or fuses may be used. These devices can be designed to interrupt the circuit when an overcurrent occurs, allowing the hazard to be corrected. U.S. Pat. No. 4,347,488, the contents of which are incorporate herein by reference, shows one possible example of a conventional circuit breaker.
A ground fault can also pose a number of hazards such as risk of fire, damage to equipment, and risk of electrical shock. Additionally, over a period of time, a ground fault can waste significant energy, resulting in economic loss. A conventional circuit breaker or fuse may not detect and interrupt a ground fault, however. Therefore, it is desirable to have a circuit breaker apparatus that can protect against both overcurrent and ground fault, and to have such a circuit breaker apparatus in a compact and economical package.